1. Field of the Invention
The present invention generally relates to the field of treating degenerative disease by administering a pharmaceutically effective amount of a compound that elevates glutathione or at least one Phase II detoxification enzyme in diseased tissue. The present invention also relates to a pharmaceutical composition useful for the treatment of degenerative diseases, as well as a method of identifying agents that modulate intracellular levels of glutathione or intracellular levels of at least one Phase II enzyme in neuronal cells.
2. Background of the Invention
Enzymes of xenobiotic biotransformation belong to two families: Phase I enzymes (cytochromes P-450), which usually oxidize or reduce xenobiotics. Although their primary role is to detoxify xenobiotics, cytochromes P-450 may also generate highly reactive and toxic compounds (Miller, et al., Bioactivation of Foreign Compounds, 3-28 (1985)). The second family of xenobiotic transformative enzymes is Phase II enzymes, which usually conjugate an endogenous moiety (e.g., glutathione, sulfate) to the xenobiotic, and serve primarily a detoxification role (Jakoby, et al., J. Biol. Chem. 265:20715-20718 (1990)). Phase II enzymes are generally induced in a coordinated fashion in response to xenobiotics. Quinone reductase (QR) is also considered a Phase II enzyme because it has protective functions (Prochaska, et al., Oxidative Stress: Oxidants and Antioxidants, 195-211 (1991)), is induced coordinately with other Phase II enzymes, and is regulated by enhancer elements similar to those that control glutathione transferase (Favreau, et al., J. Biol. Chem. 266:4556-4561 (1991)).
Well-documented evidence established that feeding of certain vegetables (e.g., brussels sprouts and cabbage) modulates both Phase I and Phase II enzymes in animal tissues (Conney, et al., Fed. Proc. Fed. Am. Soc. Exp. Biol. 36:1647-1652 (1977); Sparnins, et al., J. Natl. Cancer Inst. 66:769-771 (1981); Sparnins, et al., J. Natl. Cancer Inst. 68:493-496 (1982); Aspry, et al., Food Chem. Toxicol. 21:133-142 (1983); Bradfield, et al., Food Chem. Toxicol. 23:899-904 (1985); Salbe, et al., Food Chem. Toxicol. 24:851-856 (1985); Whitty, et al., Food Chem. Toxicol. 25:581-587 (1987); Ansher, et al., Hepatology 3:932-2935 (1983); Ansher, et al., Food Chem. Toxicol. 24:405-415 (1986)) and stimulates the metabolism of drugs in humans (Conney, et al., Fed. Proc. Fed. Am. Soc. Exp. Biol. 36:1647-1652 (1977); Pantuck, et al., Clin. Pharmacol. Ther. 25:88-95 (1979); Pantuck, et al., Clin. Pharmacol. Ther. 35:161-169 (1984)). The elevations of enzymes that metabolize xenobiotics and scavenge free-radicals may be highly relevant to the chemoprotective effects of vegetables, since relatively modest dietary changes not only affects the metabolism of drugs (Ansher, et al., Food Chem. Toxicol. 24:405-415 (1986)) but also modifies the ability of carcinogens to cause tumors in rodents (Tannenbaum, et al., Adv. Cancer Res. 1:451-501 (1953); National Research Council, Diet, Nutrition and Cancer (1982); National Research Council, Diet and Health: Implications for Reducing Chronic Disease Risk (1989); Creasey, Diet and Cancer (1985); Knudsen, Genetic Toxicology of the Diet (1986); Longnecker, et al., Cancer 47:1562-1572 (1981); Fullerton, et al., Proc. Am. Assoc. Cancer Res. 29:147 (1988); Li, et al., Cancer Res. 50:3991-3996 (1990)).
In degenerative diseases, which are generally characterized by progressive morphological changes and progressive loss in normal metabolic activity in the cells of the tissue, it is believed that oxidative stress may play an important role in the etiology of the diseases. Thus anti-oxidants, which function to scavenge free-radicals and thereby prevent oxidative damages to cells, may provide an opportunity to treat or prevent the progression of degenerative diseases. Additionally, if a treatment can act as an anti-oxidant to the cells, as well as induce Phase II enzymes, which also protect the cell from free radicals, this treatment would provide a two-pronged attack on the progression of degenerative diseases. To date, no such compounds have been identified.
The invention relates to a method of treating a subject in need of treatment of a degenerative disease, which comprises administering to the subject a pharmaceutically effective amount of a compound that elevates glutathione, or at least one Phase II detoxification enzyme, in the diseased tissue of the subject.
The invention also relates to a method of inhibiting cell death in neuronal cells, which comprises treating the neuronal cells with an agent that increases levels of glutathione, or intracellular levels of at least one Phase II detoxification enzyme.
The invention also relates to a method of identifying agents that modulate intracellular levels of glutathione or intracellular levels of at least one Phase II enzyme in neuronal cells, which comprises treating the neuronal cells with an agent, assaying for intracellular levels of glutathione or intracellular levels of at least one Phase II detoxification enzyme, and comparing these levels to control levels.
The invention also relates to a method of identifying agents that modulate intracellular levels of glutathione or intracellular levels of at least one Phase II enzyme in neuronal cells comprising comparing the levels of the intracellular glutathione or intracellular levels of at least one Phase II detoxification enzyme to determine if the agent modulates intracellular levels of glutathione or intracellular levels of at least one Phase II detoxification enzyme.
The invention also relates to a method of modulating intracellular levels of at least one Phase II detoxification enzyme in neuronal cells. The method comprises treating the neuronal cells with an agent that binds to glutathione to form a complex. The complex modulates the intracellular levels of at least one Phase II detoxification enzyme.
The invention also relates to a composition for use in the treatment of a degenerative disease, which comprises a pharmaceutical excipient and a pharmaceutically effective amount of an agent that increases intracellular levels of glutathione or at least one Phase II detoxification enzyme.